The application of steel in acidic media faces a big challenge due to the corrosion problem. Quaternary Ni-W-Cu-P alloy act as a potential coating material applied to acidic media because of its superior corrosion resistance. However, mechanism of deposition and corrosion of Ni-W-Cu-P coating plated on the surface of steel component is rare in the previous studies. In this work, the Ni-W-Cu-P coatings were deposited onto carbon steel 65Mn substrates via electroless plating. The anti-corrosion properties of the coatings in room and warm acidic solution (20%H₂SO₄) were evaluated by dipping and electrochemical test, respectively. Their deposition mechanism, composition and structure were investigated using SEM, EDS and XRD, respectively. The results show that the Ni-W-Cu-P coating is composed of spherical and block particles in the early stage of electroless plating, which are gradually transformed into spherical and strip cellular structure with the increasing electroless plating time. With prolonging electroless plating time, the Ni and W contents in the Ni-W-Cu-P coatings increase logarithmically and lineally, respectively. However, the Cu content decreases logarithmically, the P content reaches the maximum value after electroless plating for 60 min and then gradually decreases. The Ni-W-Cu-P coating is amorphous when it is annealed at low temperature, upon increasing the annealing temperature to over 400 ℃, it gradually transforms from amorphous to crystalline. The thermal stability of Ni-W-Cu-P coating can be significantly improved by co-depositing tungsten and copper element. Corrosion resistance of the amorphous coating annealed at 400 ℃ is better than that of amorphous coating as-plated and nanometer crystalline coating annealed at 500 ℃ in both room and warm acid solution. As-plated coatings and those annealed at 400 ℃ are found to corrode selectively, while pitting is observed to be the main corrosion mechanism of coatings annealed at 500 ℃. With increasing the corrosion time, the corrosion rates and corrosion current densities of the Ni-W-Cu-P coatings increase, however, their impedance values decrease.